Fluorine-containing polymers can exhibit various properties that are not performed by polymers containing other atoms. Those properties include low refractive index, low dielectric constant, water- and oil-repellency, low hygroscopicity, chemical resistance, non-adhesiveness, low frictional properties, and electrical insulation properties. Those properties may vary depending on their structures and fluorine contents.
A most common method of synthesizing such fluorine-containing polymers is a method of conducting radical polymerization of fluorine-containing monomers. However, the kinds of generally available fluorine-containing monomers by synthesis are not sufficient, and those monomers, except for some of them, generally have low reactivity. Specifically, there is a significant limitation on the structure of the polymer that can be synthesized according to the radical polymerization of the fluorine-containing monomers.
As means to solve this problem, there are known methods of reacting a variety of polymers synthesized by a variety of methods with fluorine gas to obtain a fluorine-containing polymer. Typically, U.S. Pat. No. 4,076,916 and JP-A-2002-95862 (“JP-A” means unexamined published Japanese patent application) disclose methods of fluorination by direct contact of a solid polymer with fluorine gas. Those methods, however, fail to achieve homogeneous fluorination of the entire polymer, because fluorination of the surface of the polymer preferentially occurs. International Publication WO 90/03353 discloses an example in which a polymer is fluorinated in a liquid phase. The raw materials used are, however, hydrocarbon polyethers each having a molecular weight of about 2,000, and the document lacks an example that is applied to polymers having higher molecular weights. This is probably because such a high molecular weight polymer has low solubility in a fluorinated solvent, whereby the reaction does not proceed sufficiently. As a possible solution to this, JP-A-2002-332309 describes an example in which a fluorine component is introduced into a side chain of a polymer to improve the solubility of the polymer in a fluorinated solvent, whereby fluorination of a polymer having a relatively high molecular weight is achieved. However, the fluorine content of the produced polymer is not always satisfactorily high.
As described above, no synthesis method has been known, which easily and conveniently produces fluorine-containing compounds having various structures and high fluorine contents.